Well, not knowing how your form in Excel was created, hard to tell you how.
If the extra pieces are objects like text boxes, control buttons, ect., you
can go into each of their properties and turn off the "Print Object" option
for them.
If you want to use the form to gather data and don't want any text, colors,
etc that are on the form to print, and assuming you've got it set up so that
the data fields print on the right place on your pre-printed forms, you could
do this:
Copy the forms sheet as a new sheet in the workbook. Clear it of everything
except row/column sizing (so that data still prints in proper locations).
Then where the data needs to be put a link back to the original sheet, so as
an example, there's something in A5 on the forms sheet that needs to be
printed, put a link (using proper sheet name) in A5 on this empty sheet with
='Form Sheet'!$A$5
same for other data cells. Print the blank sheet instead of the forms sheet?